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MG TD TF 1500 - Wiring Harness Installation Report

Thanks to the info in the archives of this BBS, I was empowered to install a new wiring harness in my TD this weekend. I got the new harness from British Wiring (www.britishwiring.com) and found it to be a real quality product, with all of the connectors already attached (at a much better price than the major suppliers).

I did the job at a friends house, who also has a TD and is a very good mechanic himself. He had already rewired his TD years ago. It is very helpful to have a properly wired TD on hand for reference, especially for wire routing questions.

The job took us two full days with both of us working full time, mostly on different items. After this time, the car runs, the lights and dynamo work and I was able to drive it home. I still have to get the directionals working (I have a used DB10 relay box that I suspect). So far we seem to have got the wiring right the first time.

I used someone's suggestion to label all of the wires first. This took several nights with the wiring diagram and a multimeter, verifying every wire, but is why it worked the first time.

Another tip that helped was bringing up the system using a battery charger and not the battery. You can get some false scares with this method also. We were testing the brake lights and tripped the relay on the charger. I forgot the running lights were also on, and we drew too much power. Also, I was surprised that the SU electronic fuel pump couldn't get enough power from the charger to pump/tick, leading me to think there was a problem. It ran fine from the battery.

I was pleased to find that there were metal clips along the bottom of the frame that the harness just slipped into, making the front to back routing easy.

I cut the old harness at the firewall and then from the inside of the car, fed all of the long skinny wires to the front and back of the car through the firewall, then finally the control box and fuse box wires. Then one bunch goes to the center dash panel and another out the passenger side firewall to the fuel pump/horns.

Special care needs to be taken on getting the wiring at the rear routed right. My car was wrong, but my friends provided a template.

So all in all, I would say that this has got to be one of the easiest cars in the world to rewire. The harness is for the most part completely in the open and accessible. If you fold down the outer dashboard and hold it with some C-clamps clamped to the under dash, wiring the dashboard is easy.

I would highly recommend it to anyone who has an old loom in bad condition, as mine was, or to add directionals, as I have done. Just make sure that you allow enough time. I believe that if I had done the job entirely by myself it would have taken 5 days, but I wouldn't have worked as hard and I would have taken breaks, which we didn't do.

Thanks to everyone on the BBS who has posted the wiring tips over the years. The archive was a real help and gave me the courage to think it was something I could do myself.

Larry
L Ayres

Thanks for the inspiration, Larry. I have that task in front of me.

Cheers,
Allen
Allen Bachelder

Larry - Great report! People facing this job would be well advised to print this out and follow your suggestions. Having worked in electronics for 40 years on US Naval vessels, I have been a strong advocate of labeling the wires at each end of the harness to make identification while laying on one's back under the car or the dash. Another method of protecting the harness during initial testing is to put a 10 or 15 amp fuse in series with the ground cable to the battery. This will allow most of items in the car to work (the pump doesn't like the pulsed voltage from a battery charger), while protecting the wires from incinerating themselves if a short exists. Cheers - Dave
David DuBois

Larry,

When I helped a friend wire a MK II TD last year, we tried feeding the wire from the firewall to the interior. Needless to say, it was much easier to try it your way, from the interior to the exterior, which we eventually discovered. Another thing we did was remove the steering wheel, seats, speedometer and tach cables, and then tilted the instrument fascia forward. That made working on the turnsignals and connecting up the dash much easier. We sat on throwable boat cushion!

One modification I'm considering on my car is to install a short heavier gauge red wire between the ignition switch and a bullet connector, and make all the red connections at the bullet connector.

Congratulations on getting your car wired!
Dave Braun

A late merry Christmas and a Happy New yearfrom me to all of you.
Re Wiring harness to the dash. I have plans this winter to connect the wiring on the dash to the harness with a plug. this will give me easy access to the backside. Just unplug and take the hole dash into the livingroom and work in front of the TV, not missing anything of the stupid things going on in the world. I am a lacy and stiff person of 70.
Regards Thoralf Norway
t g sorensen

This thread was discussed between 26/12/2007 and 27/12/2007

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